Adhere Cake Board To Styrofoam?

I am going to attempt to make a Scooby Doo Mystery Machine Van for my cousin's 9th bday. I would like to place a 3" styrofoam square under the van to raise it off of the base board. I will adhere the stryofoam to the base board using double sided tape. Should I just use the same to adhere the board that the actual cake is on to the styrofoam square or is there a better method? TIA.